1. Field of the Invention
The present invention relates to a video signal conversion apparatus which converts an input video signal so as to be displayable on a display apparatus with a high picture quality.
2. Description of the Related Art
Video signals of film source based on movies or films are often contained in video signals of standard television systems such as the NTSC format. The movie or film consists of 24 frames per second. On the other hand, the video signal of the standard television system consists of 30 frames per second, and it is a video signal of interlaced scanning in which one frame is constituted by 2 fields. Since the numbers of frames per second are different, the frames of the movie or film are usually subjected to television-cinema conversion by a 2-3 pulldown scheme so as to obtain the video signal of the standard television system.
With the 2-3 pulldown scheme, the first and second fields of the first frame of the video signal are created from the first frame of the movie or film, the first and second fields of the second frame and the first field of the third frame of the video signal from the second frame, and the second field of the third frame and the first field of the fourth frame of the video signal from the third frame. Regarding the subsequent frames, the video signal is created for 2 fields, for 3 fields, for 2 fields, for 3 fields, . . . from the successive frames of the film by similar conversion steps.
In this way, the movie or film is converted into that video signal of the standard television system in which the 2 frames of the former correspond to the 5 frames of the latter, and in which the video signal of 2 fields and the video signal of 3 fields are alternately repeated in correspondence with the frames of the movie or film.
Meanwhile, in a case where a picture based on the video signal of interlaced scanning subjected to the television-cinema conversion in this manner is displayed by a display apparatus such as PDP, the above-mentioned third frame, for example, in the successive frames of the video signal is formed of the combination between the pictures of the second frame and third frame of the movie or film. This has posed the problem that the video signal is inferior in picture quality to the original movie or film. It has been necessary for coping with the problem to discriminate whether an input video signal is a video signal of film source or a video signal of so-called “video source” unlike the video signal of film source, and to execute the process of picture quality adjustment for the video signal of film source.
In this regard, however, there has been the problem that the discrimination concerning whether or not the input video signal is the video signal based on the film source does not stably operate in some cases, due to the differences of the signal supply sources of input video signals, so a good picture quality is sometimes unobtainable.